Near UV (Lambda 290-400 nm) from sunlight is responsible for many biological effects, human skin cancer, killing of aquatic microorganisms, etc. Solar UV-B of Lambda greater than 300 nm contributes the majority of the injurious action of sunlight, the longwave UV-B Lambda 300-320 nm, is much less efficient per quantum than are radiations strongly absorbed in DNA UV-C, Lambda 200-280 nm). Assessment of the role of solar UV in human disease and evaluation of the human and ecological actions of ozone depletion require knowledge of the actions of the individual components of near UV, the development of instrumentation needed for such knowledge is the goal of this proposal. The low biological efficiency of the components of solar UV requires intense monochromatic sources for near UV action spectroscopy. Mercury-xenon arcs plus monochrometers provide high intensity at the mercury emission lines; however, 6 nm bandwidths are common and the mercury lines leave critical gaps in the spectral coverage. A tunable flashlamp pumped dye laser combined with frequency doubling crystals can generate near UV for action spectroscopy, a source is presently functional but needing considerable further development to reach its full potential. A program for improving and optimizing the laser operation involving, dye selection and mixtures, solvents, liquid filters, thermal stabilization, doubling crystal techniques and direct lasing at wavelengths greater than 320 nm is proposed, also including preliminary studies on feasibility of the facility as a Biotechnology Resource.